There are many chemical compounds which must be manufactured through special chemical processes. Such compounds are typically useful for various industrial purposes worldwide, but have only a limited occurrence in nature. The synthesis of these compounds typically requires a large number of steps, a large amount of energy, and the formation of intermediate by-products that are often of to value or are useless or even harmful to the environment. Therefore, in order to reduce energy consumption and the number of intermediate steps needed prior to reaching a final product, it would be advantageous in the industrial chemical arts to provide simplified synthesis processes for various useful chemical compounds.
Presently three industrial processes are used for manufacturing sodium carbonate (i.e. Soda Ash). The Solvay process uses limestone (calcium carbonate, CaCO3) and salt brine (sodium chloride, NaCl) as raw materials, and ammonia (NH3) as an intermediary, and is the prevailing process used in Europe and many other regions. The overall chemical equation for the Solvay Process can be written as:CaCO3+2NaCl→Na2CO3+CaCl2  (Equation 1)
However, in order to reach the end products, the Solvay process involves many intermediate steps. First, calcium carbonate (limestone) is heated to release carbon dioxide:CaCO3→CaO+CO2  (Equation 2)
The remainder of the process is centered about a large hollow tower. At the top of the tower, a concentrated solution of sodium chloride and ammonia enter the tower. As the carbon dioxide bubbles up through this solution, sodium bicarbonate is produced and precipitates according to the following equation:NaCl+NH3+CO2+H2O→NaHCO3+NH4Cl  (Equation 3)
The sodium bicarbonate, separated by filtration, is then converted to sodium carbonate by heating it, which also releases water and carbon dioxide:2NaHCO3→NaCO3+H2O+CO2  (Equation 4)
Calcium hydroxide is then produced by reacting the calcium oxide generated in Equation 2 with water:CaO+H2O→Ca(OH)2  (Equation 5)
From here, the ammonium chloride produced in Equation 3 is treated with the calcium hydroxide produced in Equation 5 mainly to recover the ammonia which is recycled:Ca(OH)2+2NH4Cl→CaCl2+2NH3+2H2O  (Equation 6)
In addition to producing Soda Ash (i.e. sodium carbonate, see Equation 4), the Solvay process also generates calcium chloride as a by-product (see Equation 6). While calcium chloride has a number of uses, most notably as a road de-icing agent, typically the manufacturers of Soda Ash have a major issue disposing of this by-product. For example, in seaside locations such as Saurashtra, Gujarat, India, excess calcium chloride is deposited into the sea; or in Osborne, South Australia, after it was observed that calcium chloride was silting up the shipping channel, the practice of dumping it into a settling pond was adopted.
Another well-known process for manufacturing sodium carbonate is Hou's process. This process is advantageous where a supply of carbon dioxide is available but sources of limestone (i.e. calcium carbonate) are distant. In this process carbon dioxide (produced by such processes as steam reforming) is passed through a nearly saturated solution of sodium chloride and ammonia, much like the Solvay process (see Equation 3, above). However, after removal of the precipitated sodium bicarbonate (NaHCO3), the remaining solution is cooled to allow the precipitation of ammonium chloride (NH4Cl), which can be sold as a fertilizer after removal from the cooled solution. Because the ammonia and sodium chloride need to be replenished, Hou process plants need to be located near ammonia production facilities.
In the United States, the discovery in Wyoming and California of major sodium carbonate deposits in the form of the mineral Trona has led to the gradual replacement of synthetic Soda Ash production, partially in an effort to lessen the environmental impact of calcium chloride (from industrial Solvay process plants) polluting the ground water at plant site landfills. There are also Trona mines in Turkey and in Lake Magadi in Kenya. Purified Soda Ash produced by refining mined Trona ore can be shipped to paper and glass factories and for use in various chemical and petrochemical plants. For example, purified Soda Ash is typically shipped from mines in Wyoming and California to eastern and southern U.S. states, mostly by rail.
While the mining of Trona ore is one solution to synthetically manufacturing Soda Ash, the economic cost of transporting the purified Soda Ash across the country becomes a major consideration. And while synthesizing Soda Ash locally would be the preferred solution, current synthesis processes such as the Solvay process have their own economic and environmental problems, associated with the supply of reactants and the disposal of by-product calcium chloride and the economics of the scale requiring rather large plants to produce soda ash using the Solvay process.
In light of the above, it is apparent that there is a need in the art for a more economically and environmentally friendly process for the production of Soda Ash. U.S. Pat. Nos. 8,715,477, 9,309,133 and 9,315,398, which are all by the current inventor A. Yazdanbod and are incorporated herein by reference in their entireties, teach processes and devices for Ion Separation and Recomposition Technology (ISART). ISART involves synthesizing new chemical compounds that traditionally have been hard to construct, by exchanging oppositely charged ions from one chemical compound for those of another. The ISART inventions described in the patents listed above can also be used for desalination of water by selective removal and depletion of ions. With ISART, in its many variations, it is now possible to separately remove charged ions from a first electrolyte solution and selectively recombine these charged ions with oppositely charged ions from a second electrolyte solution to form new chemical compositions in one or two steps.
In light of the above discussion regarding the production of Soda Ash, it would be advantageous to employ certain applications of ISART technology to produce needed industrial chemical compounds such as Soda Ash. It would also be advantageous to provide a chemical production process for Soda Ash which uses less energy than current Solvay or Hou processes and does not include the production of calcium chloride. It would likewise be useful if an industrial plant producing Soda Ash has no by-products requiring disposal. It would further be advantageous if an industrial plant producing Soda Ash can be located near points of consumption, to significantly reduce transportation costs. It would also be useful if such a plant could have flexible production, capabilities to adjust to varying market demands. It would further be advantageous if the polluting and greenhouse gas carbon dioxide could be utilized by a novel process to produce Soda Ash.